(1) Field of the Invention
The present invention relates to remote detection of acoustic events. More specifically, the invention relates to an automated system for detecting aircraft including a detection unit deployed from an aircraft or missile to a remote surface location. The detection unit can store and/or relay processed data to a monitoring authority.
(2) Description of the Prior Art
The desire to detect the presence of aircraft is well known. It has also been proposed to identify and locate detected aircraft based on acoustic or seismic data. For example, U.S. Pat. No. 5,721,712 to LaPointe discloses an aircraft detection system for a submarine having a rotatable acoustic antenna array, including several radially separated microphones, mounted on a submarine mast. The microphones relay acoustic signals to a signal processor for detection and location of an aircraft based on triangulation. The signal processor is said to match the acoustic signature to classify the aircraft.
U.S. Pat. No. 4,322,828 to Hoff et al. discloses a jet aircraft maneuver classifier. A geophone capable of detecting seismic signals is provided proximate an airfield used by jet aircraft. To classify aircraft activity in terms of taxi, take-off and fly-over, seismic signals are amplified and filtered to pass only two signal envelopes, i.e., of a low and a high frequency range. Maneuvers are classified by comparing the times each of two signal envelopes reach a predetermined amplitude threshold.
U.S. Pat. No. 4,408,533 to Owen et al. discloses an acoustic or seismic target ranging system to provide a munition firing signal when a target reaches its closest approach. The system utilizes a single signal detector located on a munition for measurement of signal magnitude and frequency. The closest approach of a target is determined by comparing absolute signal magnitude to the rate of change of signal magnitude.
U.S. Pat. No. 5,060,206 to DeMetz, Sr. discloses an acoustic aerobuoy detector for detecting propeller-driven aircraft. A floating buoy is provided with an exposed air resonator chamber dimensioned to amplify frequencies characteristic of distant airborne propeller aircraft. The buoy is provided with an underwater cable for transmission of an amplified signal to an underwater craft or surface craft for processing by an on-board signal processor.
The prior art, however, does not meet current needs. For example, the prior art provides no means to deploy a detection unit into a remote hostile or inaccessible environment such that monitoring can be conducted elsewhere. Further, the prior art does not provide a detection network and central monitoring authority. The present invention addresses these and other shortcomings of the prior art.
It is a general purpose and object of the present invention to provide an improved aircraft detection system. It is another object of the present invention to provide an automated aircraft detection system for detecting aircraft landing and takeoff.
It is another object of the present invention to provide a remote aircraft detection unit capable of being deployed from a missile. It is another object of the present invention to provide a remote detection unit capable of identifying a detected aircraft based on, e.g., acoustic signature.
It is another object of the present invention to provide a remote detection unit capable of processing, identifying, storing and transmitting measurement data.
It is another object of the present invention to provide a remote detection unit capable of wireless data transmission to a central monitoring authority.
It is another object of the present invention to provide a remote detection unit having improved power efficiency and advanced computing power.
It is another object of the present invention to provide a method of deploying by missile and operating an automated wireless remote detection unit.
These and other objects are accomplished with the present invention by providing a system for delivering at least one detection unit from a missile, such as a Tomahawk cruise missile in the payload dispensing configuration, to a remote surface location.
The detection unit of the present invention comprises a transducer for acquiring signals from the surrounding environment. Data samples are processed by a digital signal processor and transferred to a memory location and/or forwarded to a central authority. In a preferred embodiment, data are converted in the processor from the time domain to the frequency domain. Spectral analysis of frequency data can be accomplished by peak detection algorithms. A wireless communication system is provided for transmitting processed data to a central authority. The detection unit of the present invention is preferably also provided with a waveform library representing known aircraft acoustic signatures. Peak detection data can be cross-correlated to library data for aircraft identification. The detection unit preferably also includes a power-conserving xe2x80x9csleepxe2x80x9d mode provided by a gross audio detection circuit which remains on at all times and switches remaining unit power on and off based on a threshold ambient signal level.